package cn.bugstack.springframework.util;

import cn.hutool.core.lang.Assert;
import org.jetbrains.annotations.Nullable;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
 * 公众号：bugstack虫洞栈
 * Create by 小傅哥(fustack)
 *
 * 来自于对开源项目的学习；
 * 作者：DerekYRC https://github.com/DerekYRC/mini-spring
 */
public class NumberUtils {

    private static final BigInteger LONG_MIN = BigInteger.valueOf(Long.MIN_VALUE);

    private static final BigInteger LONG_MAX = BigInteger.valueOf(Long.MAX_VALUE);

    /**
     * Standard number types (all immutable):
     * Byte, Short, Integer, Long, BigInteger, Float, Double, BigDecimal.
     */
    public static final Set<Class<?>> STANDARD_NUMBER_TYPES;

    static {
        Set<Class<?>> numberTypes = new HashSet<>(8);
        numberTypes.add(Byte.class);
        numberTypes.add(Short.class);
        numberTypes.add(Integer.class);
        numberTypes.add(Long.class);
        numberTypes.add(BigInteger.class);
        numberTypes.add(Float.class);
        numberTypes.add(Double.class);
        numberTypes.add(BigDecimal.class);
        STANDARD_NUMBER_TYPES = Collections.unmodifiableSet(numberTypes);
    }


    /**
     * Convert the given number into an instance of the given target class.
     * @param number the number to convert
     * @param targetClass the target class to convert to
     * @return the converted number
     * @throws IllegalArgumentException if the target class is not supported
     * (i.e. not a standard Number subclass as included in the JDK)
     * @see java.lang.Byte
     * @see java.lang.Short
     * @see java.lang.Integer
     * @see java.lang.Long
     * @see java.math.BigInteger
     * @see java.lang.Float
     * @see java.lang.Double
     * @see java.math.BigDecimal
     */
    @SuppressWarnings("unchecked")
    public static <T extends Number> T convertNumberToTargetClass(Number number, Class<T> targetClass)
            throws IllegalArgumentException {

        Assert.notNull(number, "Number must not be null");
        Assert.notNull(targetClass, "Target class must not be null");

        if (targetClass.isInstance(number)) {
            return (T) number;
        }
        else if (Byte.class == targetClass) {
            long value = checkedLongValue(number, targetClass);
            if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) Byte.valueOf(number.byteValue());
        }
        else if (Short.class == targetClass) {
            long value = checkedLongValue(number, targetClass);
            if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) Short.valueOf(number.shortValue());
        }
        else if (Integer.class == targetClass) {
            long value = checkedLongValue(number, targetClass);
            if (value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) Integer.valueOf(number.intValue());
        }
        else if (Long.class == targetClass) {
            long value = checkedLongValue(number, targetClass);
            return (T) Long.valueOf(value);
        }
        else if (BigInteger.class == targetClass) {
            if (number instanceof BigDecimal) {
                // do not lose precision - use BigDecimal's own conversion
                return (T) ((BigDecimal) number).toBigInteger();
            }
            else {
                // original value is not a Big* number - use standard long conversion
                return (T) BigInteger.valueOf(number.longValue());
            }
        }
        else if (Float.class == targetClass) {
            return (T) Float.valueOf(number.floatValue());
        }
        else if (Double.class == targetClass) {
            return (T) Double.valueOf(number.doubleValue());
        }
        else if (BigDecimal.class == targetClass) {
            // always use BigDecimal(String) here to avoid unpredictability of BigDecimal(double)
            // (see BigDecimal javadoc for details)
            return (T) new BigDecimal(number.toString());
        }
        else {
            throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
                    number.getClass().getName() + "] to unsupported target class [" + targetClass.getName() + "]");
        }
    }

    /**
     * Check for a {@code BigInteger}/{@code BigDecimal} long overflow
     * before returning the given number as a long value.
     * @param number the number to convert
     * @param targetClass the target class to convert to
     * @return the long value, if convertible without overflow
     * @throws IllegalArgumentException if there is an overflow
     * @see #raiseOverflowException
     */
    private static long checkedLongValue(Number number, Class<? extends Number> targetClass) {
        BigInteger bigInt = null;
        if (number instanceof BigInteger) {
            bigInt = (BigInteger) number;
        }
        else if (number instanceof BigDecimal) {
            bigInt = ((BigDecimal) number).toBigInteger();
        }
        // Effectively analogous to JDK 8's BigInteger.longValueExact()
        if (bigInt != null && (bigInt.compareTo(LONG_MIN) < 0 || bigInt.compareTo(LONG_MAX) > 0)) {
            raiseOverflowException(number, targetClass);
        }
        return number.longValue();
    }

    /**
     * Raise an <em>overflow</em> exception for the given number and target class.
     * @param number the number we tried to convert
     * @param targetClass the target class we tried to convert to
     * @throws IllegalArgumentException if there is an overflow
     */
    private static void raiseOverflowException(Number number, Class<?> targetClass) {
        throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
                number.getClass().getName() + "] to target class [" + targetClass.getName() + "]: overflow");
    }

    /**
     * Parse the given {@code text} into a {@link Number} instance of the given
     * target class, using the corresponding {@code decode} / {@code valueOf} method.
     * <p>Trims all whitespace (leading, trailing, and in between characters) from
     * the input {@code String} before attempting to parse the number.
     * <p>Supports numbers in hex format (with leading "0x", "0X", or "#") as well.
     * @param text the text to convert
     * @param targetClass the target class to parse into
     * @return the parsed number
     * @throws IllegalArgumentException if the target class is not supported
     * (i.e. not a standard Number subclass as included in the JDK)
     * @see Byte#decode
     * @see Short#decode
     * @see Integer#decode
     * @see Long#decode
     * @see #decodeBigInteger(String)
     * @see Float#valueOf
     * @see Double#valueOf
     * @see java.math.BigDecimal#BigDecimal(String)
     */
    @SuppressWarnings("unchecked")
    public static <T extends Number> T parseNumber(String text, Class<T> targetClass) {
        Assert.notNull(text, "Text must not be null");
        Assert.notNull(targetClass, "Target class must not be null");
        String trimmed = trimAllWhitespace(text);

        if (Byte.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Byte.decode(trimmed) : Byte.valueOf(trimmed));
        }
        else if (Short.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Short.decode(trimmed) : Short.valueOf(trimmed));
        }
        else if (Integer.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Integer.decode(trimmed) : Integer.valueOf(trimmed));
        }
        else if (Long.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Long.decode(trimmed) : Long.valueOf(trimmed));
        }
        else if (BigInteger.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? decodeBigInteger(trimmed) : new BigInteger(trimmed));
        }
        else if (Float.class == targetClass) {
            return (T) Float.valueOf(trimmed);
        }
        else if (Double.class == targetClass) {
            return (T) Double.valueOf(trimmed);
        }
        else if (BigDecimal.class == targetClass || Number.class == targetClass) {
            return (T) new BigDecimal(trimmed);
        }
        else {
            throw new IllegalArgumentException(
                    "Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
        }
    }

    /**
     * Parse the given {@code text} into a {@link Number} instance of the
     * given target class, using the supplied {@link NumberFormat}.
     * <p>Trims the input {@code String} before attempting to parse the number.
     * @param text the text to convert
     * @param targetClass the target class to parse into
     * @param numberFormat the {@code NumberFormat} to use for parsing (if
     * {@code null}, this method falls back to {@link #parseNumber(String, Class)})
     * @return the parsed number
     * @throws IllegalArgumentException if the target class is not supported
     * (i.e. not a standard Number subclass as included in the JDK)
     * @see java.text.NumberFormat#parse
     * @see #convertNumberToTargetClass
     * @see #parseNumber(String, Class)
     */
    public static <T extends Number> T parseNumber(
            String text, Class<T> targetClass, @Nullable NumberFormat numberFormat) {

        if (numberFormat != null) {
            Assert.notNull(text, "Text must not be null");
            Assert.notNull(targetClass, "Target class must not be null");
            DecimalFormat decimalFormat = null;
            boolean resetBigDecimal = false;
            if (numberFormat instanceof DecimalFormat) {
                decimalFormat = (DecimalFormat) numberFormat;
                if (BigDecimal.class == targetClass && !decimalFormat.isParseBigDecimal()) {
                    decimalFormat.setParseBigDecimal(true);
                    resetBigDecimal = true;
                }
            }
            try {
                Number number = numberFormat.parse(trimAllWhitespace(text));
                return convertNumberToTargetClass(number, targetClass);
            }
            catch (ParseException ex) {
                throw new IllegalArgumentException("Could not parse number: " + ex.getMessage());
            }
            finally {
                if (resetBigDecimal) {
                    decimalFormat.setParseBigDecimal(false);
                }
            }
        }
        else {
            return parseNumber(text, targetClass);
        }
    }

    public static String trimAllWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }

        int len = str.length();
        StringBuilder sb = new StringBuilder(str.length());
        for (int i = 0; i < len; i++) {
            char c = str.charAt(i);
            if (!Character.isWhitespace(c)) {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    public static boolean hasLength(@Nullable String str) {
        return (str != null && !str.isEmpty());
    }

    /**
     * Determine whether the given {@code value} String indicates a hex number,
     * i.e. needs to be passed into {@code Integer.decode} instead of
     * {@code Integer.valueOf}, etc.
     */
    private static boolean isHexNumber(String value) {
        int index = (value.startsWith("-") ? 1 : 0);
        return (value.startsWith("0x", index) || value.startsWith("0X", index) || value.startsWith("#", index));
    }

    /**
     * Decode a {@link java.math.BigInteger} from the supplied {@link String} value.
     * <p>Supports decimal, hex, and octal notation.
     * @see BigInteger#BigInteger(String, int)
     */
    private static BigInteger decodeBigInteger(String value) {
        int radix = 10;
        int index = 0;
        boolean negative = false;

        // Handle minus sign, if present.
        if (value.startsWith("-")) {
            negative = true;
            index++;
        }

        // Handle radix specifier, if present.
        if (value.startsWith("0x", index) || value.startsWith("0X", index)) {
            index += 2;
            radix = 16;
        }
        else if (value.startsWith("#", index)) {
            index++;
            radix = 16;
        }
        else if (value.startsWith("0", index) && value.length() > 1 + index) {
            index++;
            radix = 8;
        }

        BigInteger result = new BigInteger(value.substring(index), radix);
        return (negative ? result.negate() : result);
    }

}
